1. Field of Invention
This invention relates to stormdrain pollutant-trap apparatus; and more particularly it relates to such apparatus specifically adapted to treat water-flow into existing curb-inlet subterranean drainage-chambers of an existing stormdrain-system.
2. Background of the Invention
Geo-ecologically, storm-water runoff is a natural cyclical hydrological occurrence in which more recent human activities, particularly owing to urbanization, result in often problematical changes to the natural hydrology of a watershed area. Through the ages, water has naturally percolated through pervious surfaces in which soil-filtration and biological action naturally remove pollutants; however, upon urbanization, pervious surfaces are changed by landmovers to become unnaturally reconfigured to man's needs largely as sealed-surfaces (ie: via pavement), thereby evading nature's advantageous percolation effect.
Examples of structural treatment installations include infiltration-systems, retention-basins, sand/oil-interceptors, catch-basins, and curb-inlet drainage-chambers. Catch-basins are generally connected into a stormdrain-system, and are devised to trap settled solids by means of a settling zone sump staged just below the sealed graded-surface surround directing the flow to the catch-basin inlet; and so catch-basins typically employ an uppermost grated-inlet facilitating foot and wheel travel thereover.
Drainage-chambers are also connected into a stormdrain-system having numerous such curb-inlet stations (some of which may only be catch-basins), generally empting into a town's stormdrain-system outfall-site(s) into low-lying rural areas such as beaches, rivers, streams, lakes, and marsh-like back areas of the local eco-system. Accordingly, since stormdrain systems are not typically merged with a community's underground sewer-treatment system, the early to mid 20th-century notion of simply allowing urban-runoff to be assimilated by the ecosystem, is now looked upon as seriously flawed. This runoff is generated, for example, by natural rainfall upon sidewalks, roadways, rooftops, airports, and industrial-sites. overburdened by rapid population growth, the ability of the permeable countryside to effectively assimilate environmental pollutants has essentially ended. Hence, the criticality of thoughtfully managing the polluted runoff from community businesses and street-borne contaminants such as vehicle oil-drippings, brake-dust, tire-wear particulates, and settled air-borne smog-contaminants; is becoming an obvious hazard, as we witness the pervasively declining health of our nation's ecosystem.
In 1987, the U.S. Congress added Section-402(p) to the Federal Clean-water Act, and was thus inaugurated by 40-CFR/#122/123/124 of November-1990;—a federal-statute requiring NPDES/(National Pollutant Discharge Elimination Systems)-permits for stormwater runoff discharges from municipalities and industries (including construction sites). Such NPDES-permits authorize the discharge of storm-water only, thus prohibiting (enforced by stiff fines) any pollutant contamination entering the stormwater conveyance system; which object is to virtually eliminate (or at least dramatically reduce) dependence upon our natural ecosystems for combating these man-caused pollutants from disturbing nature's normal process of dealing with mild Ph-toxicity. Moreover, it has been decreed that this thoughtful, if ambitious, governmentally overseen program be accomplished within the domains of individual United States via what is referred to as “BMP's” (Best Management Practices);—defined as any program, technology, process, siting criteria, operating method, or device, which effectively controls, prevents, removes, or reduces pollution of the ecosystem.
Because complete elimination of environmental pollution is simply not realistically feasible (ie:—unknowingly, a bucket of paint accidentally falls off the back of a truck for example), once a pollutant is generated it must be controlled; and, there are three ways of controlling pollutants in urban-runoff . . . First, via source reduction BMP's, such as through improved industrial, construction, and municipal practices which better prevent improper wastes, and by immediately cleaning-up any inadvertent contaminant-spill (recognizing that accidents do happen), and via a vigorous employee and public “anti-pollution practices” education-campaign to significantly reduce potential pollutants at the source. Secondly, via statute imposed fines for flagrant violation. Thirdly, via BMP treatment apparatus developed to decontaminate the stormdrain-runoff as best possible, and are relatively costly owing they most certainly require regular maintenance in order to remain effective.
Particularly of concern to developers of structural BMP's is the naturally intermittent action of storm events, especially the first-flush phenomenon;—wherein dry-periods without sporadic rains allow concentrations of pollutants to build-up and be flushed away from roadways as very potent concentrations in the stormwater. Thus the flushing of pollutants is especially harmful after a dryspell, because ensuing stormwaters drive the pollutants into relatively low-lying marsh and low-flow streams where they settle, inflicting further environmental damage to an already strained local ecosystem.
Such harmful environmental pollution from contaminated stormwater runoff, is associated with sediment, petro-hydrocarbon compounds, and other chemicals; all of which is terribly detrimental to micro/macro-organisms, and indulging aquatic and avian life; while the supporting base of benthic invertebrates is decimated by the very interference with the natural photosysthesis-process (ie:—respiration, growth, reproduction) vital to ecosystem survival. The stormwater sediment also carries with it toxic levels of trace metals and nutrients; all of which must be substantially captured prior to entering natural areas where wildlife must be allowed to propagate much as it has successfully for thousands of years prior to interference by man's unnatural structures.